1. Field of the Invention
The present invention relates generally to a Digital Multimedia Broadcasting (DMB) receiving terminal in a DMB system, and in particular, to a method for reducing the time required for searching for a broadcasting channel of a program selected by a user in a DMB receiving terminal.
2. Description of the Related Art
FIG. 1 is a diagram illustrating a schematic structure of a DMB receiving terminal.
A DMB terminal receives a signal transmitted by a DMB system via its radio frequency (RF) unit 115, and provides the received signal to a baseband processor 120. The baseband processor 120 converts the received signal into MPEG-2 transport stream (TS) data, and stores the TS data in a ring buffer 125. A program specific information (PSI) analyzer 135 analyzes the TS data stored in the ring buffer 125 to detect a program association table (PAT) and a program map table (PMT). After acquiring, from the detected PMT, packet identifier (PID) information of a desired audio/video packetized elementary stream (PES) of a broadcasting program, an audio/video TS (A/V TS) analyzer 130 gathers packets having a corresponding PID, and provides the packets to a decoder 140, which sequentially decodes the packets.
FIG. 2 is a flowchart illustrating a method of searching for a broadcasting channel of a program selected by a user in the conventional DMB receiving terminal.
When a user inputs a desired program number, a DMB receiving terminal detects the program number input by the user in step 212, and receives a TS packet in step 214. The DMB receiving terminal checks in step 216 whether the received TS packet has a PAT. The PAT refers to a table having information on a program, included in the currently transmitted packet, and includes a program number, audio and video constituting the program and a PID (PMT_PID) of a PMT having PIDs of packets such as a program clock reference (PCR). That is, the PAT serves to map a logical program (e.g., a particular channel) selected by the user to an actual PID.
To determine whether there is any packet having PAT information among the consecutively received TS packets, the DMB receiving terminal analyzes a header of a TS packet and determines whether its PID is ‘0’. Herein, PID=‘0’ indicates that PAT information is included in a payload.
If it is determined in step 216 that the received TS packet has no PAT, the DMB receiving terminal proceeds to step 228 where it waits for the next TS packet. However, if the received TS packet has a PAT, the DMB receiving terminal analyzes the PAT and acquires PMT_PID and program number list information in step 218. The DMB receiving terminal acquires a PMT_PID of a program number desired by the user from the PAT in step 220, and receives the TS packet in step 222. Thereafter, in step 224, the DMB receiving terminal analyzes a header of the received TS packet and determines whether the received TS packet is a TS packet corresponding to the PMT_PID. If it is determined that the received TS packet is not a TS packet corresponding to the PMT_PID, the DMB receiving terminal proceeds to step 228 where it waits for the next TS packet. However, if the received TS packet is a TS packet corresponding to the PMT_PID, i.e., if the received TS packet has a PMT, the DMB receiving terminal analyzes the PMT and detects a PID (PES_PID) of an audio/video PES constituting a corresponding program in step 226, and then ends the procedure.
Although not illustrated, upon detecting the PES_PID, the DMB receiving terminal detects an audio/video PES having the PES_PID among the TS packets received thereafter, and decodes the audio/video PES. The decoding result is provided to a display and a speaker so that the user can view and hear the DMB.
The PAT and PMT information is transmitted periodically such that the user can randomly access the terminal. For example, if the PAT and PMT information is transmitted every 0.5 seconds, the terminal requires a maximum of one second in detecting the PAT and PMT information, and the time requirement occurs not only when the terminal initially starts but also when it changes the channel. This causes the terminal user to have to wait for a considerable amount of time, leading to a decrease in terminal preference and marketability.